In a wireless telecommunications network, subscriber access units provide a wireless communication link between user PCs and a base station processor connected to a public access network. Each of the base station processors serves a wireless coverage area, or sector, defined by the physical transmission capacity of the base station processor which serves the sector. In order to provide uninterrupted service to a mobile subscriber access unit, the sectors typically have overlapping portions. As a result of the overlapping portions, a subscriber access unit may concurrently be within multiple sectors each served by a base station processor.
A subscriber access unit maintains a wireless communication link to the base station processor via a wireless session context. The session context corresponds to a plurality of connections used to provide message traffic to and from the user PCs. When a subscriber access unit is within multiple sectors, it may establish a wireless session context via the base station processor serving any of the multiple sectors. In this manner, a subscriber access unit may be served from any of the candidate base station processors which serve the multiple sectors.
Each base station processor typically serves many subscriber access units. The number of subscriber access units served by a base station processor affects the throughput of each subscriber access unit in wireless communication with the base station processor. A loading factor is indicative of a traffic load on a base station processor, and therefore corresponds to the throughput which can be provided to each processor, and therefore corresponds to the throughput which can be provided to each subscriber access unit. A high loading factor is indicative of a base station processor burdened with message traffic for many subscriber access units. Conversely, a low loading factor is indicative of an unburdened base station processor.
In a base station processor, it is computationally expensive to determine if a subscriber access unit is located in a portion of a sector which overlaps with another sector. It is further computationally expensive to determine if the loading factor corresponding to the base station processor serving the overlapping sector is less than that of the base station processor currently serving the subscriber access unit. Such determinations utilize resources that could otherwise be used for traffic through the base station processor. Accordingly, it would be beneficial to provide a subscriber access unit with the ability to determine the loading factor of each of the candidate base station processors corresponding to the overlapping sectors, and to allow the subscriber access unit to effect a session context transfer, or handoff, to the base station processor with a lower loading factor.
A system and method for transferring a wireless session context in a wireless communication network allows a subscriber access unit to transfer the session context from a first base station to a second base station depending on a loading factor which indicates the throughput load through each of the first and second base stations. A subscriber access unit which is located in an overlapping wireless coverage area of both the first base station and the second base station can transfer the session context such that it is in wireless communication with the base station having the least throughput load. Subscriber access units in overlapping coverage areas will therefore tend to transfer session context to the least burdened base station processor. In this manner, performance is improved because subscriber access units within a wireless coverage area of multiple base station processors are transferred to the base station able to provide the maximum throughput.
The wireless communication network includes a plurality of base station processors with overlapping coverage areas. Subscriber access units may be located in an overlapping coverage area served by a plurality of base station processors. Further, subscriber access units may be mobile, traveling between coverage areas and passing through overlapping coverage areas. When it is determined that a subscriber access unit is in a coverage area of more than one base station, a check is made to determine which of the base station processors corresponding to the coverage areas is least burdened by throughput. A loading factor indicative of resource utilization of each of the base station processors is computed. Each of the loading factors is compared, and the session context is transferred, or switched, to the base station having the lowest loading factor. Alternatively, the session context remains with the base station processor currently serving the subscriber access unit, if the current base station processor has the lowest loading factor. The loading factor may be computed from a variety of load parameters, and may be determined by the base station or by the subscriber access units. The loading factor may be computed at a variety of intervals, such as being initiated at uniform predetermined intervals, as a result of a loading summary sent by a base station processor, by events such as a subscriber access unit entering a new wireless coverage area, or by a loading factor approaching a predetermined threshold.